I watch how much interest is building on both sides, how often ECN/MMs change their share size or price, who's appears to actually be executing vs. posting and cancelling continuously to create the appearance of momentum, when executions print vs the inside bid and ask (especially on wide spreads) which gives an idea of which way the bid and ask are about to move towards. There's no cut and dry explanation on reading L2. It's an art that takes time to understand and experience. Once you have really reached that point then it becomes gut instinct which IMO one the best attributes I have as a trader. There have been days where I'm having some issues that are weighing on my mind that I'm not able to shake while I'm trading and it is obvious that I lose my touch reading L2 and it shows in my P&L. I learned a long time ago not to DT during those off days. Swing trading is easier because you look at charts and TA and that's cut and dry.
I went to edit a post and I hit quote instead and sent out the same post so I erased all the words to free up space...